1. Field of the Invention
This invention relates to a video signal recording apparatus which records an interlaced video signal, which forms one frame using a plurality of fields, on a recording medium using rotating heads.
2. Description of the Related Art
An explanation will now be provided illustrating a VCR (video cassette recorder) of a two-head helical scanning type as an apparatus of this kind.
In a conventional VCR, when recording a video signal which forms one frame using two fields, such as an NTSC signal or the like, the field to be recorded by one of two heads having different azimuths is in general assigned to either one of the two fields of each frame.
The reason will now be explained. In the above-described video signal which forms one frame using two fields, the phases of horizontal synchronizing signals relative to vertical synchronizing signals of the preceding field (hereinafter briefly termed a first field) and the succeeding field (hereinafter briefly termed a second field) of each frame are different from each other by a 0.5 horizontal scanning period (H). Accordingly, when, for example, performing so-called connected recording (wherein pictures recorded at different time periods are connected), if a video signal of the same field is recorded on a track immediately before the connected point of recording and on a track immediately after the connected point, the phases of horizontal synchronizing signals are not continuous at the connected point in a reproducing operation, but shift by 0.5 H. This will cause so-called skew distortion on a reproduced image surface, disturbing the image. Hence, a head having one azimuth always records the video signal of the first field, and a head having the other azimuth always records the video signal of the second field.
By thus predetermining the fields of video signals to be recorded by two heads having different azimuths, horizontal synchronizing signals continue even at connecting portions of recorded signals present in connected recording, insertion recording (wherein a picture recorded at a different time period is inserted) or the like. Hence, an image is not disturbed in a reproducing operation.
In the above-described configuration, however, the rotational phase of a rotating head cylinder having two rotating heads must be controlled in synchronization with each frame of the video signal. Hence, a long time is needed to synchronize the rotational phase of the rotating head cylinder with a desired control target phase. For example, when the head for recording the first field traces a magnetic tape, if the input video signal is the signal of the second field, the phase of the rotating head cylinder must be shifted 180.degree., and a very long time is needed until the rotating head cylinder reaches a servo-locked state. Accordingly, when performing connected recording, insertion recording or the like, the time after the video signal to be recorded has been input and the control of the rotational phase of the rotating head has been started until recording is actually started must be set long, causing a delay of the timing of recording.